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Irreducible Incoherence and Intelligent Design – a look into the conceptual toolbox of a pseudoscience

Abstract

The concept of
Irreducible Complexity (IC) has played a pivotal role in the resurgence of the
creationist movement over the past two decades. Evolutionary biologists and
philosophers have unambiguously rejected the purported demonstration of
“intelligent design” in nature, but there have been several, apparently
contradictory, lines of criticism. We argue that this is in fact due to Michael
Behe’s own incoherent definition and use of IC. This paper offers an analysis
of several equivocations inherent in the concept of Irreducible Complexity and
discusses the way in which advocates of the Intelligent Design Creationism
(IDC) have conveniently turned IC into a moving target. An analysis of these
rhetorical strategies helps us to understand why IC has gained such prominence
in the IDC movement, and
why, despite its complete lack of scientific merits, it has even convinced some
knowledgeable persons of the impending demise of evolutionary theory.

Introduction

Until
its dramatic legal
defeat in the Kitzmiller v. Dover case, Intelligent Design Creationism (IDC)
had been one of the most successful pseudosciences of the past two decades, at
least when measured in terms of cultural influence. It is interesting to
explore the way this species of creationism had achieved this success,
notwithstanding its periodic strategic setbacks as well as its complete lack of
scientific merits. Of course, a full explanation would include religious,
socio-political, and historical reasons; instead, in this paper, we will take a
closer look at the conceptual toolbox and rhetorical strategies of the ID
creationist. As a case study, we will concentrate on the central concept of
“irreducible complexity” (IC), but other examples can be found that support our
assertions. Our analysis shows that the conceptual equivocations inherent in
the concept of IC—in particular its potential to function as a moving targetin discussions (Boudry and
Braeckman 2010) —may help further our understanding
of the superficial appeal of the design argument based on IC, which is only the
most recent in a long series of creationist challenges mounted against
evolutionary theory.

Irreducible Complexity

In 1996, biochemist and
ID proponent Michael Behe introduced the infamous concept of irreducible
complexity (IC) in his book Darwin’s
Black Box. Although Behe’s critics univocally agreed that he failed to
demonstrate evidence of “intelligent design” in nature, there have been several,
seemingly inconsistent lines of criticism. Some evolutionary scientists claim
that biological systems do sometimes exhibit IC as Behe defines it, but they
deny that this poses a problem for evolutionary theory (e.g. Orr 1997;
Shanks and Joplin 1999; Miller 2000), while others maintain that Behe
has never demonstrated the existence of bona fide instances of IC in nature (e.g. Pigliucci
2002; Forrest and Gross 2007). Pennock (1999, pp.
264-272)concurs with this criticism but
grants the possible existence of biological IC systems, arguing that, in any
case, these would not threaten evolutionary theory.

We propose that this
seemingly contradictory criticism is in fact due to Behe’s own disjointed
definition and misleading use of IC. First, we introduce Behe’s concept and
briefly recount the most important empirical objections against it. Then, we
analyse the conceptual equivocations inherent in Behe’s approach on several
levels (see also
Dunkelberg 2003). Finally, we argue that these kinds
of equivocations allow Behe and his IDC fellows to make a moving target out of
their theory, hence serving to insulate it against criticism.

The Evolution of Irreducible Complexity

The concept of IC has an
interesting “evolutionary” pedigree (Forrest and
Gross 2007, p. 302). In the 1970s and 1980s,
young-Earth creationists used similar terms to describe biological systems that
were alleged obstacles to evolutionary theory. In 1974, Henry Morris, founder
of the Institute for Creation Research and father of the Creation-Science
movement, argued in his influential book Scientific
Creationism that “The problem is simply whether a complex system, in which
many components function unitedly together, and in which each component is
uniquely necessary to the efficient functioning of the whole, could ever arise
by random processes” (Morris 1974, p.
59). In 1980, young-earth creationist
Ariel Roth argued that “Creation
and various other views can be supported by the scientific data that reveal
that the spontaneous origin of the complex
integrated biochemical systems of even the simplest organisms is, at best,
a most improbable event”
(Roth 1980, p.
83). Behe has simply adapted these
creationist notions to his own ends. Consider his definition of IC in Darwin’s Black Box:

By irreducibly complex I mean
a single system composed of several well-matched, interacting parts that
contribute to the basic function, wherein the removal of any one of the parts
causes the system to effectively cease functioning. An irreducibly complex
system cannot be produced directly (that is, by continuously improving the
initial function, which continues to work by the same mechanism) by slight,
successive modifications of a precursor system, because any precursor to an
irreducibly complex system that is missing a part is by definition
non-functional. An irreducibly complex biological system, if there is such a
thing, would be a powerful challenge to Darwinian evolution (Behe 2006, p.
39).

Redundant and Irreducible Complexity

Behe then proceeds to argue that many
biological systems exhibit IC, especially at the subcellular level (e.g., the
bacterial flagellum). However, many critics have noted that the components of a
typical biological system manifest considerable functional overlaps and
redundancy. Contrary to Behe’s assertions, living systems are often quite robust
to perturbations, despite, or even because of, their complexity (Ciliberti,
Martin et al. 2007). Overall these system exhibit what
has been termed “redundant complexity” (Shanks and
Joplin 1999). For example, if we eliminate one
or even several elements from the blood clotting cascade, which Behe cites as
an instance of an IC system, the system still manages to perform its function,
albeit not as swiftly or efficiently as before. From the perspective of
evolutionary theory, this is hardly surprising; natural selection is a clumsy
and opportunistic process that tinkers with the available material. Thus, the
widespread phenomenon of redundant complexity makes it perfectly clear that
evolution by natural selection can gradually produce increasingly complex
systems without the guidance of an intelligent designer (see below).

Conceptual Double Life

To be sure, it is not difficult to find
examples of biochemical systems in which the removal of just one part damages
the whole system. But consider Behe’s phrases “effectively ceases functioning”
and “by definition non-functional.” There are two possible reconstructions of
his definition: 1) the term “functioning” refers exclusively to the basic
function currently performed by the whole system (e.g., the rotary motion of
the bacterial flagellum) and does not pertain to other possible functions, in
other contexts, when one or more components are removed; and 2) the phrases
“effectively ceases functioning” and “non-functional” include any function that
the impaired system or one of its components may perform in other contexts. In
principle, it is not very hard to discover whether a system exhibits IC in the
first, weak sense. Leaving aside the ambiguity regarding the natural “parts”
into which the system must be decomposed (Dunkelberg
2003; Sober 2008, pp. 135-160), it suffices to knock out these
parts one after the other to see if the system can still perform its basic
function. Again, evolution by natural selection is perfectly capable of
producing complex functional systems exhibiting IC in this weak sense. For
example, Lenski et al. (2003) used a population of “digital
organisms” (i.e., computer programs) to simulate the evolution of a complex
functional system. By performing a series of knockout experiments on one of the
complex functions that emerged from their simulation, Lenski et al. were able
to determine how many genomic “instructions” were involved in its functioning.
The researchers found that the function “depends on many interacting
components” (2003:141), the removal of any of which causes the system to break
down.

In fact, only an IC system in the second,
strong sense would be an obstacle to evolutionary theory, because it would rule
out evolutionary precursor systems and function shifts of the system’s
components. However, it is hard to see how Behe could even begin to demonstrate
the existence of such a system without defaulting to the classical “argument
from ignorance” (Pigliucci 2002,
p. 67). Interestingly, Behe has
disingenuously taken advantage of this very ambiguity in answering his critics.

In his initial definition, Behe seems to intend
the weak interpretation, but he then proceeds to use the concept in a line of
reasoning that only makes sense under the strong interpretation. Precisely
because the bacterial flagellum is IC, Behe tells us, it could not have evolved
by means of random mutation and natural selection. However, when critics object
that the system’s components may well be able to perform other functions in
other contexts, thus pointing to the possibility of indirect evolutionary
pathways, Behe switches back to the weak definition and claims that his critics
have misrepresented his argument.

A Conceptual Mousetrap

Robert Pennock (1999, p. 267) objected to Behe’s design argument
that “even if a system is irreducibly complex with respect to one defined basic
function, this in no way implies that nearby variations might not serve other
nearby functions”. Reasonably, Pennock construes Behe’s argument in a sense
that is intended to preclude any functional intermediate on a direct or
indirect evolutionary path to the current system:

Behe claims that there could never be any functional intermediates that
natural selection could have selected for on the way to any irreducibly complex system, but he can’t get the empirical
conclusion from his “by definition” conceptual argument” (Pennock 1999,
pp. 267-268)

Pennock’s reasoning is
correct, of course, but in the afterword to the tenth anniversary edition of Darwin’s Black Box, Behe (2006, p. 258) retorts that “Pennock [simply]
substituted his own concept of irreducible complexity for mine,” whereupon he
shifts back to the weak version of the concept, which merely rules out direct
improvements on the system: “On the contrary, on page 40, I point out that,
although irreducible complexity does rule out direct routes, it does not
automatically rule out indirect ones” (see also
Ratzsch 2005). Thus, Behe protests that Pennock
has “overlooked important qualifications” (Behe 2001, p.
707) and has simply “constructed his own
rigid straw man definition for IC.” But Behe himself has boldly stated that any
IC system is a “powerful challenge to Darwinian evolution” (2006, p. 39), and that “[w]e know of no other
mechanism, including Darwin’s, which produces such complexity” (1996, p. 25). Thus, the fact that Behe’s own
qualifications are inconsistent with his boastful presentation of IC as a major
stumbling block for evolution is hardly Pennock’s problem. Behe did acknowledge
that Pennock exposed another weakness in the definition of IC, owing to its
focus on already functioning systems rather than on the evolutionary
development of such systems. Although he promised to “repair this defect in
future work” (Behe 2001, p.
695), so far Behe has not lived up to
that promise, instead seeming to ignore the problem altogether.

The neglect of evolutionary
development in Behe’s definition is hardly a trivial matter, however, and his
concession concerning indirect routes is quite an important one, which seems to
be completely absent from his original definition (see also Sober
2008, pp. 161-162). As early as the beginning of the
20th century, geneticist Herman Muller explained how biological systems that
depend on the complex “interlocking” actions of many different components could
come about by evolutionary processes: “Many of the characters and factors
which, when new, were originally merely an asset finally became necessary
because other necessary characters and factors had subsequently become changed
so as to be dependent on the former” (Muller 1918,
pp. 463-464). Thus, redundant complexity can
eventually generate IC (under the weak interpretation). More recently,
biochemist and molecular biologist A. G. Cairns-Smith proposed the analogy of
“scaffolding” in the construction of an arch to explain the evolution of
systems that are IC according to Behe (Cairns-Smith
1986; see also Orr 1997; Pennock 2000). A classical stone arch is IC in
the weak sense, because the structure will collapse as soon as one removes
either the keystone or one of the other stones. The support of scaffolding is
necessary in building a stone arch, but once the arch is completed, the
scaffolding can be safely removed. In a similar vein, a biochemical structure
may have functioned as a scaffold in the evolution of an IC system before
becoming dispensable and disappearing. That is, “Before the multitudinous
components of present biochemistry could come to lean together they had to lean
on something else” (Cairns-Smith
1986, p. 61).

Behe has performed a
similar conceptual sleight of hand in dealing with the objections of molecular
biologist Kenneth Miller (2000). Miller accepts that some
biological systems are IC as Behe defines it (weak version), but he objects to
the anti-evolutionist conclusions that Behe derives from IC. As a
counterexample of Behe’s claim, Miller offers a plausible reconstruction of the
evolutionary history of the five-part auditory apparatus in mammals, which he
argues fulfils the definition of IC. Miller demonstrates that the individual
parts of the auditory apparatus—mallens, incus, and stapes—evolved from the
rear portion of the reptilian jaw. It is important to note that before they
migrated to the middle ear and were adapted for their new purposes, these
structures were indeed perfectly functional. Therefore, Miller concludes that
Behe’s statement (2006, p. 39) that “any precursor to an
irreducibly complex system that is missing a part is by definition
non-functional” is plainly wrong. Millerchallenges strong IC and demonstrates the crucial point, which is that
the “interlocking necessity [of the parts of the final working system] does not
mean that the system could not have evolved from a simpler version” (2000, p. 139).

Behe, however, has
responded by asserting that Miller “concocted his own, private definition of
irreducible complexity, and then argued against that” (2006, p. 259). It is quite possible, he goes on
to explain, that individual components of an IC system can perform functions in
different contexts. Thus, according to Behe, (2006, p. 260) Miller has “redefined irreducible
complexity to mean that none of the component parts of an IC system could have
its own function separate from the system”.

Yet again, the
equivocation is in Behe’s definition, not in Miller’s criticism. Bearing in
mind that Behe treats IC as if it were an insurmountable obstacle for
evolution, which is already clear from the very wording of the term
“irreducible,” the critic naturally confronts Behe’s claim of
“non-functionality” by pointing to the different functions performed by
evolutionary precursors of IC systems, which may or may not have contained
parts of the current system.

After all, if we bear in
mind that biological systems can be adapted over the course of evolution for
another function than that for which they were originally selected—for
instance, by being integrated as part of a new system performing a different
function—then Behe’s non-functionality claim becomes either trivial (weak
version) or plainly wrong (strong version).

Dembski’s Conceptual Remedy

In No Free Lunch (2002), Behe’s creationist ally William Dembski
proposed to remedy the conceptual problems of IC. Dembski believes that the
concept of IC is “salvageable” (2002:280), and after a series of
modifications, he arrives at the following new definition:

Definition ICfinal – A system performing a given basic
function is irreducibly complex if it
includes a set of well-matched, mutually interacting parts such that each part
in the set is indispensable to maintaining the system’s basic, and therefore original, function. The set of these
indispensable parts is known as the irreducible
core of the system (Dembski 2002,
p. 285, emphasis in original).

Accordingly, Dembski argues, the IC
of a system is a straightforward empirical question:

Individually knocking out each protein constituting a biochemical system
will determine whether function is lost. If it is, we are dealing with an
irreducibly complex system (Dembski 1999,
p. 148).

Clearly, Dembski has “fine-tuned”
the concept of IC in the direction of the weak interpretation, restricting the
definition to the basic, original function of the system. His updated version
has the merit of conceptual clarity (but see Perakh
2002), but, in remedying Behe’s
conceptual ambiguity, Dembski actually takes the sting out of the whole
argument. IC thus conceived is perfectly consistent with indirect and
circuitous routes, scaffolding, and exaptations. So what is all the fuss about?
The collapse of IC in Dembski’s hands illustrates that the conceptual ambiguity
he was trying to salvage was actually very convenient
for Behe.

Never Enough

Despite Dembski’s remedy,
other equivocations in the concept of IC have yet to be resolved. Having failed
to provide an objective criterion that makes evolutionary accounts impossible,
the IDC proponent retreats to a weaker probabilistic claim; as the number of
individual components in an IC system increases, the plausibility of a gradual
succession of slight modifications becomes vanishingly small. “The strength of
the inference depends on the number of parts, and the more intricate and
sophisticated the function, the stronger is our conclusion of design” (Behe 2006, p.
265). Leaving aside the problems regarding
this alleged correlation between the numbers of parts and the strength of the
design inference, which are amply documented by Pennock (1999, p. 270), we still seem to be left with a testable statement. If we can find a
well-functioning precursor for one of the systems discussed by Behe (or for one
of its components), or if we can construct a plausible evolutionary pathway for
one of Behe’s examples, the “probability” argument collapses.

Behe’s claim has indeed
been tested against the facts and has been found wanting (Miller 2000;
Lenski, Ofria et al. 2003; Young and Edis 2006; Forrest and Gross 2007). In response to these
demonstrations, however, IDC proponents belatedly “reinterpret” their initial
claims in order to lift them out of the critic’s reach. A first strategy to
this end consists of shifting the burden of proof from plausible evolutionary
pathways to the actual evolutionary story, and thus to protest that the broad
outlines of a plausible evolutionary account amount to nothing more than
Darwinian wishful thinking and speculation. The same bait-and-switch technique
can be discerned here: IC is constantly boasted as a point of principle for
ruling out the possibility of evolutionary explanations, but as soon as it is
challenged on that ground through a discussion of plausible evolutionary
scenarios, ID creationists contend that they were talking about actual
evolutionary pathways all along.

When they are confronted
with tangible evidence of actual evolutionary history, IDC theorists resort to
a second strategy, shifting their design claims to the remaining parts of the
evolutionary puzzle, as if the “real” problem was always there. For example,
Kenneth Miller (2004) beautifully demonstrated the
structural similarities between one component of the flagellum and the
so-called type III-secretory system. He convincingly argued that the former is
a very plausible evolutionary precursor of the latter, which has been co-opted
by evolution to perform a new function (see also Pallen
and Matzke 2006). In response to this embarrassing
demonstration, Behe (2001, pp.
689-690) simply shifted his attention to the
complexity of the newly discovered system by itself, while at the same time
stubbornly insisting that the assemblage of these precursors into the flagellum
system is still impossible without the helping hand of a Designer (Behe 2004, p.
359).

In light of these
evasions, one may wonder whether there is any amount of comparative genetic
evidence, or any level of evolutionary reconstruction, that would make Behe and
his allies abandon their design claims. Because of the sloppiness of the
probabilistic IC claim, which is not based on any serious quantification of
probabilities, IDC theorists can continue to raise the evidential bar up to a
point where the concept of IC is lifted outside of the empirical domain
altogether. Indeed, when pressed on the available scientific knowledge of a
particular complex system that he cites, Behe has made it clear that only a
complete, quantitative, and fully-detailed description of what actually happened over the course of the
ages would convince him of its evolutionary origin (Behe 2007). In his testimony at the Dover
trial, Behe conceded:

Not only would I
need a step-by-step, mutation by mutation analysis, I would also want to see
relevant information such as what is the population size of the organism in
which these mutations are occurring, what is the selective value for the
mutation, are there any detrimental effects of the mutation, and many other
such questions. (2005, p. 19)

But this is an absurd demand, which
is never met in any other scientific domain, and is certainly not met by ID
creationists themselves when they propose “design” as an alternative
explanation. Indeed, despite his demand for such a high level of evidence for
the evolution of what he claims are IC systems, Behe himself has been
completely unwilling to flesh out his design hypothesis to any degree at all,
insisting that the motives and character of the designer are in fact
inscrutable, and he provides us with no clue as to his modus operandi. As for Behe’s request for fully detailed knowledge
about evolutionary history, Pigliucci (2002, p. 240) has warned biologists not to be
overconfident in taking up creationist challenges, and not to mistake partial
reconstructions and plausible scenarios for a complete understanding of
evolutionary development. Indeed, evolutionary theorists are better advised to
explain why the burden of proof insisted on by creationists is absurd, and to
point out that scientific knowledge will never be complete in this respect.

In any case, what is
disingenuous in Behe’s presentation is that this preposterous challenge to
offer a complete and step-by-step evolutionary account of IC systems is not
spelled out from the beginning, but is a belated revisionof his original claim, based on ambiguities in his definition of
IC. In Darwin’s Black Box, Behe
leaves us with the impression that the unevolvability claim of IC is in
principle easy to challenge, but when his critics take up the gauntlet, as we
saw in the discussion with Pennock and Miller, Behe simply dodges and weaves
like a hunted rabbit. Thus, what remains of Behe’s argument boils down to the same
old “argument from personal incredulity” (Dawkins 1991,
p. 38), which is a far cry from the
“objective criterion” for design that IDC theorists had promised.

It is interesting to
note that the same pattern of reasoning has always been rampant in traditional
creationist arguments regarding the so-called “gaps” in the fossil record.
Creationists claim that they would readily accept evolution if only the
“missing links” between the taxonomic groups turned up in the fossil record,
but, whenever such a fossil is found, they complain that the intermediate is
not really the ancestor of the present organism—an impossible demand for the fossil
record—or even that Darwinists now face an ever bigger hurdle, because they are
left with two gaps to explain. The latter principle has been coined “Gish’s
law” by geologist Robert S. Dietz (1983), after young-earth creationist
Duane Gish.

Falsification and Failure of Instantiation

The
design argument based on IC always allows for a final retreat. Suppose we can
provide IDC proponents with a fully-detailed description of the evolution of
the bacterial flagellum. Even if their stubborn insistence on the flagellum’s
exhibiting IC would at that point become absurd even in their own eyes
(although one can never be too sure about that), they would surely regard this not
as a refutation of IDC as such, but merely as a specific case in which IC turns
out not to be instantiated. The expectation that this particular biological
system would exhibit IC and hence be one of those unmistakable traces of design
would simply be disappointed, and the search for new obstacles to evolution
could begin.

In fact, this is what the history of
the creationist movement is all about: if the case for evolution by natural
selection becomes too overwhelming, creationists typically drop their favourite
examples of complexity and come up with fresh ones, whose evolutionary origins
are still relatively obscure (Pennock 1999,
pp. 171-172). For example, the traditional
objection against evolution used to be the vertebrate eye. Nowadays, the
evolutionary development of the vertebrate eye is well-understood and it has
become an outdated argument against evolutionary theory. It is not even a
particularly difficult example for evolutionary theorists, as it involves
relatively straightforward selection pressures.

As the evolutionary
history of the bacterial flagellum and the blood clotting system are being
unravelled, the next generation of creationists can always disclaim the
examples of their IDC forebears, and a new round of pointless arguments can
begin—although they would at least have to admit that their former “design
criterion” was defective because it generated false positives. However, the retreat into unknown
territory cannot go on indefinitely. In fact, as Robert Pennock (1999, p. 171) remarked, the current preoccupation
of IDC theorists with invisible biochemical niceties such as the propeller
system of E. coli bacteria indicates
“just how far creationists have had to retreat to find significant explanatory
gaps in evolutionary theory”.

Moving the Goalposts

The most conspicuous
feature of the concept of IC is not so much its ambiguity, but the discrepancy
between what it seems to promise and what it eventually delivers, as far as
testable empirical claims are concerned. On first reading Behe’s argument, the
unsuspecting reader may be left with the impression that Behe really sticks his
neck out and presents evolutionists with a clear empirical challenge. However,
this apparent rigour of the IC concept as an objective criterion for design,
which arguably makes it appealing to anti-evolutionists, evaporates upon closer
inspection. Under the weak interpretation, the concept describes a well-known
phenomenon in the living world that is unproblematic for evolutionary theory.
Under the strong interpretation, IC systems would indeed confront evolutionary
theory with serious problems, but Behe has not given us an inkling of how we
could ever demonstrate whether a system qualifies as IC in this sense. Indeed,
it would require ruling out any conceivable evolutionary history, and would
thus amount to showing that no part or precursor of the system in question is
able to perform any other function, in any other situation and at any time.

This allows for an
interesting bait-and-switch strategy, which one could summarize as follows:
“First, present evidence for weak IC in the living world, then pretend that
strong IC has been demonstrated and continue to equate IC with
‘unevolvability.’ If challenged on empirical grounds, jump back to the weak
version and claim that your critics are misrepresenting your argument. Switch
the IC claim to subsystems and assembly of components, keep raising the
standards of evidence, and reassert that all this directly follows from the
simple objective criterion of IC. Finally, when really pressed against the
wall, give up this particular system and quickly find a new one. Repeat the
circle ad libitum.”

Further Equivocations

Behe’s concept of IC is
not the only instance of conceptual equivocation in the IDC literature. Two
examples may be the subject of further research. First, when writing about
“information,” William Dembski surreptitiously switches between its standard
interpretation in information theory, in which it is a measure of the
randomness in a system, and its colloquial use in the sense of “meaningful
message” (Perakh 2004,
pp. 64-75). This ambiguity allows him to fool
the reader into believing that the “information” encoded in DNA, for example,
points in the direction of an intelligent designer. For a similar discussion
regarding the term “teleological”, see Blancke et al. (2010).

A second example is the
IDC response to the series of mousetraps that John McDonald devised to refute
the claim that gradualist evolution of IC systems is impossible (with the
mechanical mousetrap as a paradigm example). Instead of admitting to their lack
of imagination, IDC theorists have responded by complaining about the
intelligent guidance used in constructing this evolutionary progression of
mousetraps (Behe 2004, pp.
364-366). Amazingly, they argue that
McDonald’s mousetraps unwittingly demonstrate that an IC system always requires
an Intelligent Designer. But this reply illegitimately shifts the
discussion—which is actually about a human artifact and thus is, in any case,
irrelevant—from the IC of a system to the blind and unguided character of
evolution.

Conclusion

Although the IDC
movement has been damaged, in terms of its credibility, by the Kitzmiller v.
Dover case, it does not show clear signs of disappearing. As Forrest and Gross
note in an afterword to their meticulous study of IDC’s politics and religious
ideology, the movement has simply changed its strategy once again. After their
recent legal setbacks, they have been forced to drop overt talk of “intelligent
design” and to adopt code words like “academic freedom” and teaching “the
strengths and weaknesses of evolution” instead (Forrest and
Gross 2007, p. 337). “Creationists never give up. They
merely change their strategy with each new defeat” (Forrest and
Gross 2007, p. 309).

As was apparent from its
conception, the rapid success of the IDC movement was never drivenby its arguments but by its religious
ideology, which was epitomized in the so-called Wedge document of IDC’s home
base, the Discovery Institute (Forrest and
Gross, 2007b). Beyond religious motivation, one
can point to sociological, cultural, and political factors to account for the
remarkable success of IDC (outside the scientific community, to be sure), and
it is plausible that the persistence of anti-evolutionary sentiments and the
continuing appeal of the design argument is also a function of deeply rooted
cognitive dispositions and hard-to-shake teleological intuitions about the
world (Kelemen, 2004;
Kelemen and Rosset, 2009).

Anti-evolutionism can
take many different forms, however, and not all of them can achieve equal
cultural success. In this paper, we have analyzed some of the rhetorical
strategies that Behe and other IDC theorists have used for presenting their
challenge to evolution and for deflecting valid criticism. On the one hand, we
claim that Behe’s presentation of IC has the appearance of an objective design
criterion, which makes it superficially more respectable than the age-old
“argument from personal incredulity.” On the other hand, the equivocations that
are built into the definition of IC allow it to be used as a moving target (Boudry and Braeckman, 2010), and as a kind of conceptual
chimera that is hard to pin down by critics. These considerations partly
explain why the concept of IC was hailed by the movement as the ultimate
challenge to evolutionary theory, and why, despite its complete lack of
scientific merits, it has convinced even some knowledgeable persons of the
impending demise of evolutionary theory. As Robert Pennock (1999:1) wrote:

We think of creationism as a cluster of ideas that reproduces itself by
spreading from mind to mind and struggling with competing ideas for a home
among a person’s beliefs. Sometimes it loses out to more powerful rival ideas,
but sometimes it finds receptive mental soil, takes root and waits to be passed
on again.

Indeed, in the past two decades the
concept of IC seems to have found receptive mental soil among
anti-evolutionists. An analysis of the convenient conceptual equivocations
inherent in IC, as well as of the rhetorical strategies with which IC has been
presented, helps us to understand this remarkable fertility.

Bibliography

Kitzmiller vs Dover
Area School District. Transcript of proceedings. Afternoon session (U.S.
District Court for the Middle District of Penssylvania 2005)

Behe MJ (1996,
October 29) Darwin Under the Microscope. The New York Times, p. 25,